The present invention relates to an exhaust gas cleaning device for an internal combustion engine, more particularly, to an exhaust gas cleaning device provided with a filter member which collects particulates in the exhaust gases an an electrically heating means which heats and burns the particulates collected by the filter member.
Since the fuel consumption of diesel engines is small, they have been recently employed as engines for vehicles.
However, diesel engines discharge a large amount of carbon particulates, that is smoke as compared with gasoline engines. Therefore, such an exhaust gas cleaning device as to decrease the amount of the smoke, has been required in the diesel engines.
Conventionally, an exhaust gas cleaning device provided with a filter member for collecting carbon particulates in the exhaust gases and an electric heater for raising the temperature of the exhaust gases entering the filter member and burning the particulates collected by the filter member has been proposed.
For example, U.S. Pat. No. 4,211,075 discloses the device provided with a grid-shaped electric heater which is disposed in the exhaust gas passage on the upper stream side of the filter member at a distance therefrom.
However, according to this divice, the heater firstly heats the exhaust gases and then the heated exhaust gases heat the filter member and the particulates collected by the filter member so that heat applied to the heater is liable to be loosen due to radiation loss. And according to this device, the whole amount of exhaust gases is heated so that a larger amount of electric power is required for heating the exhaust gases to a combustion temperature of the particulates.
And another device provided with a plurality of heaters which are disposed on the inlet end surface of the filter member or adjacent thereto, has been also proposed.
However, according to this device, a leading wire for each heater is liable to contact with another one and the structure for retaining a plurality of heaters and for disposing the leading wires thereof is complex. Furthermore, when the flow quantity of the exhaust gases is large, heat of the heater is not effectively transmitted to the particulates collected by the filter member.
Accordingly, one object of the present invention is to provide an exhaust gas cleaning device for an internal combustion engine, comprising an electric heater which can effectively burn and eliminate the carbon particulates collected by the filter member by a small amount of electric power consumption.
Another object of the present invention is to provide an exhaust gas cleaning device for an internal combustion engine, comprising an electric heater which is stably attached by a simple attaching structure.